Keywords: soil and water conservation, yield increase, cost-benefit, watershed management, food security.

Transcription

1 20 years of watershed management in Niger: approaches, impacts and economic aspects of large scale soil and water conservation measures Nill, D.; Ackermann, K; Schöning, A.; Trux, A.; van den Akker, E.; Wegner, M. 1 1 GIZ, Eschborn, Germany. s: dieter.nill@giz.de, klaus.ackermann@giz.de, alexander.schoening@giz.de, anneke.trux@giz.de, elisabeth.akker-van@giz.de, martina.wegner@giz.de ABSTRACT: For more than 20 years, German Development Cooperation (GIZ/KfW) has been fighting desertification in the South of Niger. More than 400,000 ha of private and communal lands have been treated with a range of different soil and water conservation and restoration (SWC/R) techniques and adjacent communities trained to put them to use. The programme has been implemented with intensive participation of the population, who contributed a major part of the work. Today the programme has become one of the largest SWC/R-programmes of German Development Cooperation worldwide. Long-term measurements of yields and biomass in farmers fields showed sustainable grain yield increases of around 200 kg/ha and straw yield increases of around 500 kg/ha. Herbaceous biomass production measured on formerly completely degraded laterite plateaus increased by 600 to 700 kg/ha after treatment. Calculations of costs and benefits indicate positive annual returns for most techniques. However, treatment of fields has been economically more viable than treatment of unfertile communal plateaus due to lower investment costs, higher productivity of fields and reduced management complexity. Under economic aspects, applying soil and water conservation/restoration measures at the landscape scale should, therefore, preferably focus on fields while large-scale treatment of communal plateaus should be undertaken if important side-benefits are likely to be achieved, such as protecting underlying fields, irrigation areas or settlements or specific production of high value crops (i.e. Arabic gum). Within fields, SWC/R techniques need to be combined with agronomic measures e.g. use of manure in order to produce optimum economic returns. In semi-arid areas, climate-change induced reduction of rainfall may change the function of sylvo-pastoral land-use to water harvesting areas for water provision to underlying fields. Keywords: soil and water conservation, yield increase, cost-benefit, watershed management, food security. 1. INTRODUCTION The combination of natural and man-made influence has led to severe land degradation in the Sahel since the 1960ies. Climate change has caused higher temperatures and declining, less reliable rainfall patterns with severe droughts during the 70ies and 80ies. A population growth rate of 2 to 3% exacerbates pressure on farm land, pastures and forests. The natural vegetation cover has gradually been reduced through deforestation, overgrazing and reduced fallowing, leaving soils unprotected to water and wind erosion. High runoff and soil loss rates in combination with insufficient organic matter inputs reduce soil fertility and favour the formation of gullies. In addition, ground water levels have dropped accelerating the decline of woody vegetation and the drying up of wells. Sealed soils prevent vegetation growth and completely drop out of production, which in turn increases pressure on the remaining agricultural land. Since 1986, German Development Cooperation (GIZ, KfW) has been supporting the populations of four departments north of the capital of Niamey, Niger, in its fight against desertification. Private fields as well as communal grazing and forest areas have been treated with a range of different soil and water conservation and restoration (SWC/R) techniques. Management regulations for restored communal lands have been developed with a view to defining more sustainable use patterns for pastures and trees. In terms of geographic coverage, the programme is one of the largest SWC/R programmes of German Development Cooperation worldwide. It has been implemented with the intensive participation of the population, who voluntarily provides all manual labour as own contribution. The programme contributes significantly to food security. 2. APPROACH AND TECHNIQUES The programme has developed a rolling approach to work with villages. The first year serves for organizing the villagers, for planning and training. Intensive implementation takes place from the second through to the fifth year. In years five and six, management responsibility is progressively transferred to the villages and proramme support ends after year six. In order to receive support for the improved management of their private and communal lands, villages have to submit a request to the programme.. Based on participatory diagnostics of a village, the programme approves or declines its support. The population commits to providing free manual labour, local materials and to ensuring the maintenance of all investments. The programme provides training, basic tools, transport and tractor-ploughing of plateaus. In the first year, the villagers establish their development committee with several sub-committees i.e. for treatment of fields, reforestation and management of communal areas. In a participatory land-use planning process, the different landscape units of the village territory are identified and suitable conservation measures defined according to three units i.e. fields (mainly situated 1

2 on the foot hills), slopes and plateaus (figure 1). The annual activities are decided on by each village in a bottom-up planning Valley Bottom Hill foot Slope Plateau SWC mesures Stonebunds Permeable rock dykes Grass strips Planting pits (tassa, zaï) Mulching, compost Manual trenches Permeable rock dams Stonebunds Half-moons Nardi/Vallerani trenches Figure 1: Typical toposequence and applied SWC measures process. First pilot activities with SWC/R measures are carried out and used for training of villagers. Extension agents of the programme are based in the villages to train and support the population (1 agent per 4-5 villages). By 2010, the programme had worked in 24 out of 29 municipalities in the four departments, covering 343 villages. SWC/R measures are applied according to the different land units and soils of topo-sequences within a village area. The fields are typically situated on the lower slopes and hill foots. They are treated mostly with simple stonebunds consisting of three stones. On very sandy soils, grass strips are used. Permeable rock dykes are used to treat gullies in the fields. Furthermore, farmers are advised to use straw mulch and compost in the fields and planting pits to restore soils. Slopes and plateaus are used for extensive grazing. The grass and woody vegetation of the plateaus is used for grazing, fire wood and collection of fruits and medicinal products. Slopes are treated in parts with hillside trenches, permeable rock dykes and stonebunds. Tractors with Nardi-Vallerani ploughs treat the shallow, poor and stony soils (laterite crusts) of the plateaus establishing trenches of 4 to 6 m long and 0,5 m wide. Between strips of nardi trenches, the soil is ripped to a depth of 10 cm. Nardi trenches are planted with trees (planting or direct seeding). Grass is seeded on the ripped strips between the nardi trenches. Areas on plateaus that are not accessible by tractors are treated with manually constructed half-moons. In total, more than 400,000 ha have been treated with different techniques by In order to monitor costs and benefits of different techniques, yields of millet grain and straw have been continuously monitored since 1996 on around 50 fields with treatments and compared to adjacent untreated fields in order to avoid reductions in measurement validity due to differences in rainfall. In each field, measurements were taken on three plots of 10 x 10 m (above, below and in the middle of stonebunds). On plateaus, 200 m transects were established. Herbaceous and woody vegetation were measured on 30 to 40 transects. Costs and benefits were analysed based on yield and biomass measurements between 1998 and Results Grain yields in farmers fields were more than doubled by using stonebunds, which are mostly combined with the application of compost and/or mulching. Surplus grain yield was around 200 kg/ha (table 1). Increases in straw yield amounted to about 525 kg/ha or a factor of 1.6. After 15 years of measurements, no decline in surplus yield had occurred showing the long-term sustainability of the effects. Plateaus constitute a difficult environment for vegetation growth due to their shallow, stony soils. Yields of herbaceous biomass were limited to between 600 and 700 kg/ha for most years (table 2). Production of wood, as measured in a number of sites, generally amounted to around 1 stere per year. It is interesting to note that the additional straw production in the fields (525 kg/ha) represents around 80% of the additional herbaceous biomass production of the plateaus ( kg/ha). 2

3 Table 1: Mean grain yield of millet on fields with and without stonebunds Indicator Mean grain 1996 to 2003 Mean grain 2006 to 2010 Mean straw 2009 and 2010 (1) Grain yield of untreated control plot (kg/ha) (2) Grain yield of treated field (kg/ha) (3) Straw yield of untreated control plot (kg/ha) 942 (4) Straw yield of treated field (kg/ha) (5) Surplus production (kg/ha) (6) Multiplication factor [(1) / (2) and (4) / (3)] x2.0 x2.4 x1.6 (Source: Poeyry/Particip 2010 ; Poeyry 2011 ; Particip 2005) Table 2: Herbaceous biomass yield (kg/ha) on untreated and treated plateaus Indicator Mean for period to 2003 Untreated sites (kg/ha) 57 - Treated sites (kg/ha) *1 *1 average of seven sites in Ouallam (Source: Poeyry 2011 ; Particip 2005) The results of the treatments on different plateaus depended strongly on the quality of management by the local village development committee i.e. the level of application of initial grazing bans, the limitation of grazing intensity and consistent tree management. Results of two independent qualitative assessments indicate that about 20% of the sites were well maintained, around 50% were of medium quality and 30% were weakly managed (table 3). Table 3: Qualitative assessment of plateau sites Study by: Number of assessed Assessment of site quality sites Good Medium Degraded Koné (2011) 19 21% 47% 32% Kusserow (2010) 18 16% 56% 28% (Source : Poeyry, 2011) 4. COST AND ECONOMIC VIABILITY The initial investment costs for the treatment of plateaus have generally been higher than those for treatments carried out in the fields (table 4) due to the significant deployment of manual labour (construction of trenches, half-moons) and heavy machinery (tractor, plough). Mechanical treatment (nardi trenches) has been more cost-effective than manual treatment and allows for restoration of large areas (~ 1ha/h for nardi plus ripping), which could not be achieved with manual labour alone. In fields, the establishment of half-moons is expensive due to the high labour requirements. In comparison to other techniques, stonebunds are low cost even if trucks are used for transport. Their costs can still be significantly reduced if donkey carts are used. Donkey carts are a viable option if stones are found within a 1 km radius. Their introduction offers additional advantages for transporting manure, harvest produce and water. Planting holes are slightly more expensive than stonebunds. Their advantage is that they can be used without any external input and if no stones are available in close proximity. Their high labour requirements also limit the area that can be treated. Most of the treatment costs are taken over by the local population who provides manual labour and local materials (seeds, manure) free of cost. Table 4: Initial investment costs and contribution from the population (based on analysis of data ) Treatment of fields Unit investment cost (FCFA/ha) Contribution of population (%) Stonebunds (truck) % Stonebunds (donkey cart) % Half-moons * % Planting holes * % Treatment of plateaus Half-moons + tree plantation * % Manual trenches * % Nardi trenches + ripping + grass % and trees *5 *1 300 units/ha plus initial application of 5t/ha of manure, * holes/ha, *3 625 units/ha, *4 625 units/ha, *5 400 units/ha and 800 trees 3

4 The annual investment and recurrent costs and benefits are presented in table 5. Total annual costs include the annual depreciation (initial investment divided by the lifetime of the infrastructure) and the annual recurrent costs (labour and input costs for agricultural production, maintenance, replanting of trees etc.). The total production value was calculated from grain and straw production of millet (fields) and herbaceous and wood production on plateaus. Table 5: Annual benefit of different treatments (data ) Treatments of fields Life Total annual time (yr) cost 1 (FCFA/ha) Surplus grain (kg/ha/yr) Surplus straw (kg/ha/yr) Value surplus grain + straw 2 (FCFA) (1) (2) (3) (4) (5) (6) = (4)*100 + (5) * 20 Annual benefit (FCFA) (7) = (6) (3) Stonebunds (truck) Stonebunds (donkey cart) Stonebunds (truck) + manure Agricultural half-moons + manure Planting holes + manure Treatments of plateaus Biomass (kg/ha) Wood (steres/ha) Forestry half-moons + tree plantation , Manual trenches , Nardi trenches + ripping + grass , seeding (Source: Particip, 2005) 1 Annual cost includes depreciation of the investment (investment costs divided by life time) plus annualy recurrent costs for labour, maintenance, agricultural operations and inputs (1 labour day = 800 FCFA, tractor plus plough FCFA/h, truck 472 FCFA/km). 1 ~ 650 FCFA, 1 US$ ~ 500 FCFA 2 Price of millet: 100 FCFA/kg, straw and biomass: 20 FCFA/kg, wood: FCFA/stere The results show that only small annual returns are derived from the treatment of plateaus when compared to the returns derived from the treatment of fields. This is due to the high initial investment and annual recurrent costs in relation to the comparatively low productivity of plateaus. Half-moons with planted trees (forestry half-moons) or used for millet production (agricultural halfmoons) are not economically viable. Treatment of fields generally results in positive returns except for half-moons. In order to generate high returns, infrastructure and agronomic measures have to be combined (i.e. stonebunds + manure). Planting holes combined with manure application, for instance, ensure high returns and can be established by the population without significant external investment. Labour input requirements, however, are rather high in relation to the comparatively short lifetime of the measure (2 years), limiting their applicability to smaller areas only. 5. CONCLUSIONS Treatment of fields with simple stonebunds and planting holes in combination with some fertilization are low cost, economically viable options suited to approximately doubling grain and straw yields thereby improving food security for the population and fodder availability for its livestock. With an investment between and FCFA (~ 20 to 60 $US) per hectare, around 200 kg additional grain can be produced, which approximately equals the annual grain requirements of one person. Large-scale treatment of sterile plateaus offers lower economic returns in terms of fodder and wood production. The management of such treated communal areas has proven to be more complex and only partially successful. The major part of the herbaceous biomass produced on plateaus can also be produced in the fields as straw. In the same vein, wood production can be substituted by agroforestry techniques in the fields. Under economic aspects, investments in soil- and water conservation should therefore rather focus on the treatment of fields. Treatment of communal plateaus should address specific objectives beyond general watershed treatment, biomass and wood production. Only additional benefits from protecting underlying fields or irrigation schemes from gullying and sedimentation, plantation of woody species with additional value beyond fire wood (e.g. Acacia senegal for arabic gum, trees for medicinal use, fruit species, timber) and/or special biodiversity objectives may justify the investment. In areas with decreasing rainfall, plateaus may gain importance as water harvesting areas for low-lying fields, which would require techniques to collect and channel the water from the plateaus to the fields. 6. REFERENCES Particip (2005). Le système de formation, l efficience de réalisation et les effets des mesures anti-érosives ainsi que l influence sur la stratégie long terme, 71 pp, KfW, Germany. Poeyry/Particip (2010). Suivi des réalisations et résultats de la Direction Régionale FICOD-Ti. 32 pp, FICOD/KfW, Niger. 4

5 Poeyry (2011). Suivi des réalisations et insertion des mesures antiérosives dans une approche communale. 72 pp, FICOD/KfW, Niger. (Source : edzard.nebe@lahmeyer.com) 5